Part A
AT45DB642D-TU
Adesto Technologies
- Lifecycle
- Active
- Stock
- 6357 PCS
- Package
- TSOP-28
- Series
- Memory
Replacement verdict
Compatible functional replacement candidate
The AT45DB321D-TU and AT45DB642D-TU share an identical package, pinout, supply voltage range, and DataFlash serial interface, making them functionally interchangeable in most designs. The primary distinction is memory density, with the AT45DB642D-TU offering double the capacity of the AT45DB321D-TU. Designers should confirm that system firmware and addressing accommodate the larger page and array size before substituting the higher-density device.
Package Type
High match
Supply Voltage Range
High match
Interface Type
High match
Memory Density
Validation required
Parts at a glance
Part B
AT45DB321D-TU
Adesto Technologies
- Lifecycle
- Active
- Stock
- 2290 PCS
- Package
- TSOP-28
- Series
- Memory
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AT45DB321D-TU | AT45DB642D-TU | Why it matters |
|---|---|---|---|
| Memory Density | 32 Mbit (4 MB) | 64 Mbit (8 MB) | The second device offers twice the storage capacity, which directly determines whether the part can hold the required firmware or data image. |
| Page Size | 512 bytes per page | 1056 bytes per page | Page size affects write granularity and buffer usage; firmware written for one page size may not map directly onto the other without code changes. |
| Number of Pages | 8192 pages | 8192 pages | Page count combined with page size defines total density and the address range the controller must support. |
| Supply Voltage Range | 2.7 V to 3.6 V | 2.7 V to 3.6 V | Both parts operate over the same voltage range, so power supply compatibility is maintained when substituting. |
| Interface Type | SPI (Serial Peripheral Interface) | SPI (Serial Peripheral Interface) | A shared SPI interface means the host controller can communicate with either device using the same bus protocol. |
| Maximum Clock Frequency | 66 MHz | 66 MHz | Identical maximum clock rates ensure comparable read/write throughput and timing budget compatibility. |
| Package / Mounting | 28-TSOP, Surface Mount | 28-TSOP, Surface Mount | Matching package and footprint allow a drop-in board-level replacement without PCB redesign. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Equivalent industrial temperature ratings confirm both parts suit the same environmental conditions. |
| Organization | 2 banks of 4096 pages | 2 banks of 4096 pages | Bank organization affects concurrent read-while-write behavior and the addressing scheme used by firmware. |
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Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AT45DB642D-TU | AT45DB321D-TU |
|---|---|---|
| Part Status | Obsolete | Obsolete |
| Memory Type | Non-Volatile | Non-Volatile |
| Memory Format | FLASH | FLASH |
| Technology | FLASH | FLASH |
| Memory Size | 64Mb (1056 Bytes x 8192 pages) | 32Mb (528 Bytes x 8192 pages) |
| Memory Interface | SPI | SPI |
| Clock Frequency | 66 MHz | 66 MHz |
| Write Cycle Time - Word Page | 6ms | 6ms |
| Voltage - Supply | 2.7V ~ 3.6V | 2.7V ~ 3.6V |
| Operating Temperature | -40°C ~ 85°C (TC) | -40°C ~ 85°C (TC) |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the key differences between the AT45DB321D-TU and AT45DB642D-TU DataFlash memory devices?
The primary difference is memory density: the AT45DB321D-TU provides 32 Mbit (4 MByte) of serial DataFlash memory, while the AT45DB642D-TU provides 64 Mbit (8 MByte). Both are manufactured by Atmel (now Microchip Technology) and are offered in the same 28-pin TSOP package (TSOP-28, 8 x 14 mm). The AT45DB642D-TU also supports dual-interface operation (Serial Peripheral Interface and RapidS), whereas the AT45DB321D-TU is a standard SPI-compatible device.
Are the AT45DB321D-TU and AT45DB642D-TU pin-compatible?
Yes. Both devices are supplied in the same 28-pin TSOP Type I package with the same pinout, including SI, SO, SCK, CS, RESET, WP, and VCC/GND positions. This allows a common PCB footprint; however, firmware must account for the different page sizes and densities before substituting one for the other.
What are the page sizes and organization of each device?
The AT45DB321D-TU is organized as 8,192 pages of 528 bytes each (512 bytes main memory plus 16 bytes SRAM buffer per page). The AT45DB642D-TU is organized as 8,192 pages of 1,056 bytes each (1,024 bytes main memory plus 32 bytes SRAM buffer per page). Both devices include two SRAM data buffers to support continuous read-while-write operation.
What supply voltage and clock frequency do these devices support?
Both the AT45DB321D-TU and AT45DB642D-TU operate from a single 2.7 V to 3.6 V supply. The maximum SPI clock frequency is 66 MHz for both devices, and the AT45DB642D-TU additionally supports RapidS operation at up to 66 MHz for high-speed applications requiring continuous data streaming.
Can the AT45DB642D-TU be used as a drop-in replacement for the AT45DB321D-TU?
Hardware-wise, the devices share the same 28-pin TSOP package and pinout, so the PCB footprint is compatible. However, they are not firmware drop-in replacements: the AT45DB642D-TU has twice the density and a different page size (1,056 bytes vs. 528 bytes), so page-address calculations, buffer sizes, and command sequences must be updated in the host firmware. The design should be validated against the respective Microchip datasheets before substitution.
What are the typical applications for these DataFlash devices?
Both devices are used for code shadowing, data logging, firmware storage, and voice/data storage in embedded systems. The AT45DB321D-TU (32 Mbit) suits applications with moderate storage needs, while the AT45DB642D-TU (64 Mbit) is appropriate where larger code images or data buffers are required, such as in networking equipment, industrial controllers, and consumer electronics.
What is the operating temperature range and package type for these devices?
Both the AT45DB321D-TU and AT45DB642D-TU are specified for the industrial temperature range of -40 °C to +85 °C and are supplied in a 28-pin TSOP Type I package (8 x 14 mm). The "-TU" suffix denotes the TSOP package and industrial temperature grade per Microchip ordering conventions.